The movie players provided in Ubuntu can play back unencrypted DVDs. However, many commercial DVDs are encrypted with a weak algorithm called Content Scrambling System (CSS).You can enable playback of encrypted DVDs with MPlayer, xine and Totem-xine by installing libdvdcss2.

The CSS key sets are licensed to manufacturers who incorporate them into products such as DVD drives, DVD players and DVD movie releases.Most DVD players are equipped with a CSS Decryption module.

Installing libdvdcss2

First you need to install the libdvdread3 package using the following command

sudo apt-get install libdvdread3

Now download the libdvdcss2 library using the following command

sudo /usr/share/doc/libdvdread3/examples/install-css.sh

For Ubuntu 6.10 (Edgy Eft) users use the following command

sudo /usr/share/doc/libdvdread3/install-css.sh

If you want to download libdvdcss2 library manually you can download from here

For AMD64 Users

First you need to install the following packages

sudo apt-get install debhelper build-essential fakeroot

Now download the libdvdcss2 library using the following command

sudo /usr/share/doc/libdvdread3/examples/install-css.sh

For Ubuntu Edgy Users use the following command

sudo /usr/share/doc/libdvdread3/install-css.sh

That's it now Your DVD player should now play back encrypted DVDs.You can ope your Movie player from Applications > Sound & Video